Photographic emulsion containing fog inhibitors



Patented May 11, 1 943 I I UNITED STATES PATIENT OFFICE PHOTOGRAPH) EMULSION CONTAINING FOG INHIBITORS Samuel E. Sheppard and Waldemar Vanselow',- Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application November 28, 1939,

Serial No. 306,508

14 Claims. (Cl. 95-7) g I This invention relates to fog inhibiting agents Derivatives of these compounds which we have for photographic emulsions and to photographic found suitable as antifoggants are the following: emulsions containing them. 7-methyl-6-thiopurine This application is a continuation in part of application Serial No. 72,773, filed April 4, 1936. C Photographic emulsions, particularly ultrasensitive emulsions or those containing color H sensitizers exhibit-a tendency to fog. This fog CH presents itself as a uniform deposit of silver exfl tending over the emulsion. It may be caused by exposing the emulsion in a room which is not 4 7'methyl'zfi'dlthm' completely dark or by development of the film Purine for protracted periods or at temperatures above HN-("=S normal. Highly sensitive emulsions are more CH likely to fog than those of lower sensitivity owing l5 to the small amount of energy required to make 5: K the silver halide grain developable. on It is, therefore, an object of the present in- I vention to provide photographic emulsions of mo enhanced stability and which do not exhibit a high tendency to fog. The compounds used for z'chlompugne 7 this purpose should not markedly lower the I sensitivity of the light sensitive materials in which they are incorporated.-

Sheppard and Wightman U. S. Patent No. I 1,763,990 describes as for inhibitors or stabilizing compounds for photographic emulsions a v a L,- number of aliphatic and aromatic amides, among 7 methy1 2 6 at them malonyl carbamide. This compound has a tmmopuhhe six membered heterocyclic ringcontainingfour carbon atoms and two nitrogen atoms. TIN-0:8

We have nowdiscovered ,that certain deriva- 0K8 tives of pyrimidine containing a similar ring s= structure, namely the thiopurines and thiouracils, are valuable fog inhibitors.

Pyrimidine may be represented by the followa ing structural formula: z-thioum il N=CH HN =0 2 "H H 40- S=(|J 43H Q 'I\EH V m x-En Purine, which has the same ring structure as 2,6-dithiouracil pyrimidine, has the following structural formula; HN C=S i=3]: I 45 s=t on H main u The watersolubility of these compounds may N-C--N be increased by forming a salt with an inorganic Uracil is 2,6-dihydroxy pyrimidine, having' acid and this compound may, therefore, bemore the following structural formula: ily n r e in the emulsion- NH C=O In the preparation of an emulsion containing H the antifoggants used according to our inven- I a tion. a solution of the fog inhibitin'g agent is.

as made up in a suitable solvent, such as water gant per 1000 cc. of

an emulsion under similar conditions not containing a fog inhibiting agent.

The amount of these fog inhibiting agents added to the emulsion is of importance since if.

too much of the fog inhibiting compound is added it may desensitize the emulsion markedly. The exact amount that must be used varies with the particular fog inhibiting compound selected and with the type of the emulsion used as regards grain size and alkalinity of the emulsion and ratio of the gelatin to silver halide. However, we have found that with gelatino silver halide. developing out emulsions, the amount of antifoggant will generally vary between about .001 gram and 1 gram of antifoggant per 1000 cc. of emulsion, although the amount may be as great as 5 grams of antifogemulsion in some cases. The fog-inhibiting agents which we have found to be satisfactory may be used in various kinds of photographic emulsions. In addition to bein useful in ordinary non-color-sensitized emulsions. they may also be used in ortho-chromatic and panchromatic emulsions or in X-ray emulsions. They can be used with or without sensitizing dyes and if used with sensitizing dyes may be added to the emulsion before or after them. The following table will serve to illustrate the amounts of fog-inhibiting agents which we have found to be satisfactory, in each case the amount being used in 1000 cc. of a gelatino-silver halide emulsion containing from 5 to gelatin:

. Grams 2-thiouracil 0.001 to 1 2,6-dithiouracil .0003 to 0.3 7-methyl-2,6-dithiopurine .0005 to 0.05

'l-methyl-fi-thio-2-chloropurine .0005 to .5 7-methyl-6-thiopurine .004 to .5 i

I 7-methyl-2,6,8-trithiopurine .001 to 0.1

It is to beunderstood that more cries of the fog-inhibiting agent than the' amount stated above may be used. Generally, however, if a greater amount is used in the emulsion, either no increased fog-inhibiting effect is obtained, or there is a marked decrease in sensitivity of the emulsion.

In addition to fog-inhibiting action, some of these compounds, such as 7-methyl-6-thlopurine and '7-methyl-6-thio-2-chlorcpurine, increase the se sit v y of the emulsion to some extent.

We consider as included within our invention all modifications and equivalents coming within the scope of the appended claims.

We claim:

1. A photographic emulsion comprising a colloidal material having a sensitive silver salt dispersed therein and containing a sulfur derivative of a pyrimidine-selected from the group consisting of thiopurines and thipuracils in fog-inhibit: ing amounts.

2. A photographic emulsion comprising gelatin having a sensitive silver salt dispersed therein and containing a sulfur derivative of a pyrimidine selected from the group consisting of thiopurines and 2-thiouracils in fog-inhibiting amounts.

3. A silver halide gelatin emulsion containing a thiouracil in fog inhibiting amount.

4. A silver halide gelatin emulsion'containing a mono-thiouracll'in fog-inhibiting amount.

5. A silver halide gelatin emulsion containing 2-thiouracil in fog-inhibiting amount.

6. A photographic emulsion comprising a col.- loidal material having a sensitive silver salt dispersed therein and containing as an anti-i'oggant from about 0.001 gram to about 1 gram perliter of emulsion of a thiouracil. I

7. A photographic emulsion comprising a colloidal material having a sensitive silver salt dispersed therein and containing as an anti-foggant from about 0.001 gram to about 1 gram per liter of emulsion of Z-thiouracil.

8. A gelatino silver halide emulsion containing as an anti-foggant from about 0.001 gram toabout 1 gram per liter of emulsion of a thiouracil.

9. A gelatino silver halide emulsion containing as an anti-foggant from about 0.001 gram to about 1 gram per liter of emulsionpf 2-thiouracii.

10. A silver halide gelatin emulsion containing a thiopurine in fog-inhibiting amount.

11. A silver halide gelatin emulsion containing a G-thiopurine in fog-inhibiting amount.

12. A photographic emulsion comprising a colloidal material having a sensitive silver salt dispersed thereinand containing as an anti-foggant from about .0005 gram to of emulsion of a thiopurine.

13. A gelatino-silver ing as an anti-foggant from about .0005 to about 1 gram per liter of emulsion of a thiopourine.

14. A gelatino-silver halide emulsion contain ing as an anti-foggant from about 0.004 gram to about 0.5 gram per liter of emulsion of a 6-thiopurine.

' SAMUEL E. SHEPPARD.

WALDEMAR VANSELOW.

about 1 gram per liter halide emulsion contain- 

